Smooth, spheroidal, appendage free underwater robot capable of 5 dof motions

ABSTRACT

An underwater robot includes a body including a first end, and a second end, opposite the first end, and first and second actuation units positioned inside the body. Each actuation unit includes a pump and two valves connected to the pump. The first and second actuation units generate jets of fluid that are discharged through the first and second ends to propel the underwater robot, and the first and second ends are smooth.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. provisional patent applications 61/642,007, filed May 3, 2012, and 61/714,290, filed Oct. 16, 2012, which are all incorporated by reference along with all other references cited in this application.

TECHNICAL FIELD

The present invention relates to the field of underwater vehicles, including, more particularly, to underwater robots.

BACKGROUND OF THE INVENTION

To access complex underwater structures robots must be tetherless, compact, highly maneuverable, and have a smooth body shape with minimal appendages. These requirements are challenging because few propulsive systems can be designed to fit into a smooth, streamlined body. A moment referred to as the “Munk moment” is destabilizing for elongated bodies. For example, the moment tends to rotate them broadside to the flow.

Thus, there is a need to provide improved robotic systems and techniques.

BRIEF SUMMARY OF THE INVENTION

A new 5 degree of freedom (DOF) underwater robot is provided. This robot is propelled using a novel pump-valve system and is therefore able to achieve a smooth, symmetric outside shape. The yaw direction of the robot is stabilized using feedback control. The pitch direction is designed to be passively stable by placing the center of mass below the geometric center. The vehicle therefore does not need external stabilizers and can have a smooth outer shape. Due to its symmetry and unique design, the robot is capable of unique motions and maneuvers such as turning in place, sideways translation, and forward-stop-reverse motions. In addition, due to the propulsion system being completely internal, this robot is very quiet and creates relatively small disruptions to the surrounding fluid.

In a specific embodiment, an underwater robot includes a body including a first end, and a second end, opposite the first end, and first and second actuation units positioned inside the body, each actuation unit a pump and two valves coupled to the pump. The first and second actuation units generate jets of fluid that are discharged through the first and second ends to propel the underwater robot, and the first and second ends are smooth.

In another specific embodiment, an underwater robot includes a body having a shape of a spheroid and including a first end, and a second end, opposite the first end, a first actuation unit to propel the underwater robot, the first actuation unit being positioned inside the body and including a first pump having a first outlet, and a second outlet, a first valve coupled to the first outlet of the first pump, and a second valve coupled to the second outlet of the first pump; and, a second actuation unit to propel the underwater robot, the second actuation unit being positioned inside the body and including a second pump having a third outlet, and a fourth outlet, a third valve coupled to the third outlet of the second pump, and a fourth valve coupled to the fourth outlet of the second pump. An angle between the first and second outlets of the first pump is 90 degrees, and an angle between the third and fourth outlets of the second pump is 90 degrees.

In a specific implementation, a method includes placing a robot in water, where the robot includes first and second actuation units to propel the robot through the water, each actuation unit including a pump having two outlets 90 degrees apart, and a valve coupled to each of the two outlets of the pump, maneuvering the robot via at least one of the first or second actuation units in a surge motion, maneuvering the robot via at least one of the first or second actuation units in a sway motion, maneuvering the robot via at least one of the first or second actuation units in a heave motion, maneuvering the robot via at least one of the first or second actuation units in a pitch motion, and maneuvering the robot via at least one of the first or second actuation units in a yaw motion.

Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures.

BRIEF DESCRIPTION OF THE FIGURES

The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

FIG. 1A shows a diagram of a fin stabilizing a prior art underwater robot in a forward direction.

FIG. 1B shows a diagram of the fin destabilizing the prior art robot in a reverse direction.

FIG. 2A shows a top view of a specific embodiment of a robot having a smooth shape that is appendage free and capable of 5 DOF.

FIG. 2B shows an end view of the robot shown in FIG. 2A.

FIG. 2C shows a top view of another specific embodiment of a robot.

FIG. 2D shows a bottom view of the other specific embodiment of the robot.

FIG. 2E shows a front view of the other specific embodiment of the robot.

FIG. 2F shows a back view of the other specific embodiment of the robot.

FIG. 3 shows the vehicle body or robot fixed coordinate frame.

FIG. 4 shows a CFD illustration of a 180 degree centrifugal pump.

FIG. 5A shows a schematic of a centrifugal pump having a 90 degree configuration.

FIG. 5B shows the pump in FIG. 5A where the impeller direction is reversed.

FIG. 5C shows a CFD illustration of the pump in FIG. 5A.

FIG. 5D shows a CFD illustration of the pump in FIG. 5B.

FIG. 6A shows a schematic of a valve.

FIG. 6B shows a CFD illustration of the valve in FIG. 6A.

FIG. 7 shows an example of a prototyped valve.

FIG. 8 shows an example of a prototyped actuation unit.

FIG. 9 shows the maneuvering architecture for the robot.

FIG. 10 shows the inside of the robot.

FIG. 11A shows a forward and reverse test of the robot.

FIG. 11B shows a sway direction translation of the robot.

DETAILED DESCRIPTION

An underwater vehicle propulsion system is provided that allows a smooth, symmetric underwater robot to move with 5 degrees of freedom (DOF). Maneuvering forces and moments are provided by using internal pumps and valves to eject fluid jets through various exit ports. The degrees of freedom include surge, sway, heave, pitch, and yaw. In a specific embodiment, the vehicle is entirely symmetric and has no external appendages such as propellers or fins. The use of an internal propulsion system allows the robot to operate very quietly and create few disruptions to the surrounding fluid. These robots can be used for a variety of applications ranging from the inspection of water-filled piping structures, to exploration of underwater infrastructure and wildlife, just to name a few examples. In a specific embodiment, the robot is completely or substantially smooth yet capable of stable motions in 5 translations or rotations.

In a specific embodiment, a smooth spheroidal robot is capable of 5 degrees of freedom and has no external appendages such as propellers or fins. In this specific embodiment, the smooth outer shape and 5 degrees of freedom are achieved through the use of a pump-valve architecture based on retrofitted centrifugal pumps and fluidic valves. Angled jets are provided which enable translations in surge, sway, and allows the system to be stabilized through feedback control.

Developing these types of smooth, spheroidal vehicles is a challenging task due to the fundamental fluid mechanics. Smooth, streamlined robots are subjected to directional instability caused by the Munk Moment. For this reason, streamlined underwater vehicles often use fins at their rear to move their aerodynamic center backwards and therefore make them passively stable. However, the fins can add extra size making the robot less compact. Second, at large angles of attack, fins can add substantial induced drag that can inhibit the turning robot of the vehicle. Finally, while fins in the rear of the vehicle will stabilize the vehicle in one direction they will further destabilize the vehicle when the direction is reversed. Therefore a robot with fins will be required to turn around 180 degrees rather than simply being able to move in reverse. This limits the maneuverability and omni-directional properties of the robot. This phenomenon is illustrated with a diagram in FIGS. 1A and 1B. FIGS. 1A and 1B show how fins can provide stability in one direction (FIG. 1A) but instability in the other (FIG. 1B).

The current development presented here introduces a combination of a novel design and closed loop control that overcomes the issue of instability and addresses the shortcomings of previous systems. In a specific embodiment, a jet arrangement is provided that enables the planar robot dynamics to be fully controllable. Linear control system design techniques are used to develop a closed loop controller capable of stabilizing the robot.

To prove operability, a prototype of a robot was fully built, tested, and verified to operate as intended. FIG. 2A shows a top view of a specific embodiment of a robot 205 that was built as a prototype. FIG. 2B shows an end view of the robot shown in FIG. 2A. This prototype may be referred to as the Omni-Egg or Omni-Egg prototype. As shown in FIG. 2A, this specific embodiment of the robot includes a body or housing 208 that define an interior space 210. The body includes a first end 211, a second end 215, and an intermediate section 218. The first and second ends are opposite each other. The intermediate section is between the first and second ends. A length L indicates a length of the robot. A width W indicates a width of the robot.

There are a set of openings 221 on the body. The openings allow for the intake of a fluid, such as water, and the output of the fluid as jets which propel the robot through the fluid. More particularly, as shown in FIG. 2B, a first subset 225 of the openings can be located at the first end. A second subset of the openings can be located at the second end.

FIGS. 2C-2F show views of another specific embodiment of a robot 250 that was built as a prototype. This robot is similar to the robot shown in FIGS. 2A-2B, however, this robot does not include a separate intermediate section. FIG. 2C shows a top view of the robot. FIG. 2D shows a bottom view of the robot. FIG. 2E shows a front or first end view of the robot. FIG. 2F shows a back or second end view of the robot. A coordinate system 252 has been included with the views to help indicate the orientation of the robot. This specific embodiment includes first and second ejection openings 255A, B (FIG. 2C), third and fourth ejection openings 255C, D (FIG. 2D), fifth and sixth ejection openings 255E, F (FIG. 2E), and seventh and eighth ejection openings 255G, H (FIG. 2F). There is an intake opening 260 (FIG. 2D).

This example of the robot includes eight ejection openings and one intake opening. The number of openings, however, can vary depending on the factors such as the application of the robot, number of pumps, number of valves, desired movements (e.g., degrees of freedom), and so forth. For example, there can be fewer or more than eight ejection openings. There can be more than one intake opening. In a specific implementation, there are at least eight ejection openings.

Actuation units can be positioned inside the body that suck in the fluid and eject the fluid as jets through the openings. For example, depending on the type of motion desired fluid may be outputted through the first end, second end, or both. Further discussion of the actuation units is provided below.

The body can further house other components of the robot such as one or more cameras (e.g., two cameras), controller, RF transmitter, RF receiver, antenna (e.g., for wireless operation), power source (e.g., battery), motor, switch, storage device (e.g., hard drive or flash memory for recording images), sensors (e.g., temperature sensor, or depth sensor), lights (e.g., light emitting diodes (LEDs)), measuring instruments, collection instruments, and the like. The body can be designed to be watertight and may include seals, o-rings, gaskets, and the like.

In a specific embodiment, the body is made of plastic. Portions or sections of the body may include a transparent material so that a camera inside the body can capture images. For example, in a specific embodiment, the intermediate section includes a transparent material (e.g., transparent piece of plastic) for capturing images via the camera. Some examples of materials that the body may be fabricated or made from include polymers, nylon, rubber, carbon fiber, metal (e.g., steel, stainless steel, or titanium), glass, or combinations of these.

In a specific embodiment, the length of the robot is about 146 millimeters and a width of the robot is about 108 millimeters. The small size of the robot allows the robot to navigate through tight spaces. The dimensions of the robot, however, can vary greatly depending upon its application. For example, the length of the robot may be greater or less than 146 millimeters. The width of the robot may be greater or less than 108 millimeters.

As shown in FIG. 2A, in a specific embodiment, a shape of the robot includes a spheroid. A spheroid is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal (opposing) semi-diameters. In a specific embodiment, the shape is a prolate spheroid. A prolate spheroid has the shape of an ellipse that is rotated about its major axis. In this specific embodiment, the robot is symmetrical. A shape of the first end is the same as the shape of the second end. The shape of the first end can be a mirror image of the shape of the second end. The ends can be dome-shaped. A shape of a top half of the robot is the same as a shape of a bottom half of the robot.

The symmetry of the robot shape facilitates movement of the robot through the various directions or degrees of freedom. For example, having the shape of the first end being the same as the shape of the second end facilitates the robot's movement in a first direction (e.g., forward direction) and a second direction (e.g., reverse direction), opposite the first direction.

In this specific embodiment, the robot does not include an external propeller, fins, foils, stabilizing attachments, or other appendages that may break off or snag on obstacles. For example, an exterior surface of the robot may be smooth or substantially smooth, continuous, or uninterrupted by an appendage.

The smooth, spheroidal robot shown in FIGS. 2A and 2B is capable of 5 degrees of freedom and has a completely or substantially smooth outer shape. This design was achieved by using internal pumps which suck in water and then eject or exhaust out pressurized jets. Fluidic valves are used to control the direction of the pressurized jets. Based on the jet direction, the robot can either purely translate in the “x” (surge) direction, the “y” (sway) direction, or the “z” (heave) direction. In addition the robot can purely rotate about either the “x” (pitch) axis or the “z” (yaw) axis. An illustration of the coordinate frame is provided in FIG. 3.

In other words, the surge motion may be unaccompanied or substantially unaccompanied by the sway, heave, pitch, and yaw motions. The sway motion may be unaccompanied or substantially unaccompanied by the surge, heave, pitch, and yaw motions. The heave motion may be unaccompanied or substantially unaccompanied by the surge, sway, pitch, and yaw motions. The pitch motion may be unaccompanied or substantially unaccompanied by the surge, sway, heave, and yaw motions. The yaw motion may be unaccompanied or substantially unaccompanied by the surge, sway, heave, and pitch motions.

In a specific embodiment, an actuation unit includes a centrifugal pump for the propulsive component. Centrifugal pumps are advantageous because of their mechanical simplicity, availability at centimeter (cm) size scales, and the ease of use with electronic circuitry. However, one common issue with some centrifugal pumps is that they are not reversible. This means that the pump can only provide force in one direction and will need to be combined with a second one in order to achieve bi-directional forces. Ideally, the pump could be designed to provide forces in 2 directions 180 degrees apart. This would save substantial space and weight. An example of this geometry is provided in FIG. 4. The pump sucks water in through the plane of the page and then depending on the direction of rotation of the impeller will eject water through either Exit 1 or Exit 2. In this figure, the impeller is rotating counterclockwise and therefore is ejecting fluid through Exit 1. However, note that there is substantial flow out of Exit 2 as well. This “backflow” serves to degrade the performance of the pump by substantially reducing the output force.

Applicants have discovered that by orienting the two exit ports adjacent to each other but 90 degrees apart, problems with backflow can be eliminated or reduced. This outlet design may be referred to a “90 degree retrofit.” FIG. 5A shows a schematic diagram of a pump 505 of an actuation unit. A set of coordinate axis have been included with the figure to help indicate orientation. The pump includes an impeller 510, a suction side 515, a first exit (or first pressure side) 520, and a second exit (or second pressure side) 525.

In this specific embodiment, an angle 530 between the first exit and the second exit is about 90 degrees. That is, the angle is a right angle. In the example shown in FIG. 5A, the impeller is rotating in a counter-clockwise direction 535. As a result of the counter-clockwise direction, fluid will exit through the exit 1 (520). FIG. 5B shows a schematic diagram of the pump shown in FIG. 5A. In FIG. 5B, however, the direction of the impeller is reversed from the direction shown in FIG. 5A. That is, in FIG. 5B, a direction 540 of the impeller is in a clockwise direction. As a result of the clockwise direction, fluid will exit through the exit 2 (525).

Computational Fluid Dynamic (CFD) illustrations of the 90 degree retrofit are provided in FIGS. 5C and 5D. FIG. 5C shows the CFD illustration for the pump direction shown in FIG. 5A. Note how in this case there is no or a reduced backflow out the second exit as compared to FIG. 4. In fact a small amount of suction occurs which further improves the force output. This approach was verified and shown to provide double the output force of the 180 degree pump. FIG. 5D shows the CFD illustration for the pump direction shown in FIG. 5B.

More particularly, in a specific embodiment, the unique capabilities of the robot are enabled by three components: retrofitted centrifugal pumps, use of fluidic valves to achieve bidirectional in-line forces, and the use of angled jets to achieve multi axis forces. Each of these three components will be discussed in greater detail below.

In a specific embodiment, fluidic valves that achieve bidirectional forces are provided. While the centrifugal pumps combined with the 90 degree retrofit provide substantial forces in 2 directions, the 2 directions are 90 degrees apart rather than the desired 180. This fact complicates vehicle design. One approach is to use elbows to redirect the flow. Elbows, however, can cause substantial losses. Thus, in this specific embodiment, custom designed Coanda effect valves are provided. These valves are based on bistable fluidic amplifiers that allow switching the direction of a jet 180 degrees at high speeds.

FIG. 6A provides an illustration of how the Coanda effect valve works. A jet is supplied to inlet 1610, while control ports C1 and C2 can open to the ambient fluid or close and seal the port. If port C1 is opened while C2 is closed the jet will exit the nozzle, attach to the right side of the device, and exit through exit E2 620. A CFD illustration of the fluid jet exiting exit E2 is provided in FIG. 6B. Similarly, if C1 is closed and C2 is opened, the jet will switch and exit through exit E1 615. Note that the arrows associated with reference numbers 615 and 620 indicate exits E1 and E2, respectively, rather than the direction of the fluid output.

In a specific embodiment, Applicants have designed these valves for the specific application of water jet propulsion. Computational fluid dynamics (CFD) and experiments have allowed for miniaturizing the design. In this specific embodiment, a special switching mechanism has been designed that uses a small direct current (DC) motor. The small DC motor is used to open and close the control ports, and requires simple commercially available electronics for control.

FIG. 7 shows an example of a built, tested, and verified prototype of a valve 705 of an actuation unit. The valve includes an inlet 710, a first exit 715, and a second exit 720. An angle between the first and second exit is about 180 degrees.

One of these valves can be attached to each of the two exit ports on the retrofitted pumps. This means that now a single pump can be engineered to provide an output jet in one of two pairs of directions or 4 directions total. This full manifestation may be referred to as a 2DOF actuation unit. These units can serve as the building blocks for robots, as they can be combined and rotated in order to meet the user requirements. FIG. 8 shows an example of a built, tested, and verified fully assembled 2DOF actuation unit.

As shown in the example of FIG. 8, an actuation unit 805 includes a pump 810, a first valve 815, and a second valve 820. The pump includes a first exit port 825 and a second exit port 830. An angle between the first and second exit ports is about 90 degrees. An inlet of the first valve is connected to the first exit port of the pump. An inlet of the second valve is connected to the second exit port of the pump. The valves have been mated to the pump such that one valve is rotated 90 degrees with respect to another valve. As a result, the exits of the valves are in different planes. For example, as shown in FIG. 8 an exit 835 of the first valve is in a different plane with respect to an exit 840 of the second valve. The exit of the first valve may be in a first plane parallel to the paper. The exit of the second valve may be in a second plane perpendicular to the paper.

A specific embodiment provides for a 5 DOF underwater vehicle design using pump-valve architecture and angled jets. In this specific embodiment, this robot design incorporates two of the actuation units. An illustration of the layout is provided in FIG. 9. Pump 1 can produce Jet 2 or Jet 4 depending on direction, and Pump 2 can produce Jet 1 or Jet 3. Also note how Jets 1 and 2 are angled at their outputs. This is a key innovation of the design. This novel feature means that forces can be provided in both the “x” and “y” directions. The Omni-Egg design is capable of 5 DOF (surge (x), sway (y), heave (z), pitch (q), and yaw (r)). The coordinate frame is illustrated in FIG. 3.

For example, Jet 1 is directed through a first channel 930. The ends of the channel are angled 933A and 933B. In a specific implementation, the angle is about 30 degrees from the x-axis. The angle may range from about 15 degrees to about 45 degrees. Similarly, Jet 2 is directed through a second channel 940. The second channel may be similarly angled as the first channel. The angle of the channels allows Jets 1 and 2 to be angled at their outputs as shown by arrows 950A-B. Arrows 950A-B show the direction of the fluid jets from the robot. The angled direction of the fluid jets help to stabilize and control the movement of the robot.

During operation of the robot, the actuation units (e.g., pumps and valves) can be activated and deactivated to achieve the desired movement. In a specific implementation, Pump 1 generates one of Jet 2 or Jet 4. Pump 2 generates one of Jet 1 or Jet 3. The opening and closing of the valve control ports associated with a pump can be rapidly pulsed to achieve the desired movement.

Table A below provides a summary of maneuvering primatives for how each of these DOFs can be achieved.

TABLE A DOF First Jet Second Jet +x +Jet 1 +Jet 2 −x −Jet 1 −Jet 2 +z +Jet 3 +Jet 4 −z −Jet 3 −Jet 4 +q +Jet 4 −Jet 3 −q −Jet 4 +Jet 3 +r +Jet 1 −Jet 2 −r −Jet 1 +Jet 2 +y +Jet 1 −Jet 1 −y +Jet 2 −Jet 2

To achieve translations in the y direction, jets 1 and 2 are angled and then the high speed nature of the Coanda effect valve is used. By switching Jet 1 between positive and negative in a fast but symmetric manner, pure translation in the +y direction can be achieved because the x translations cancel out. This high speed switching is enabled by the use of the Coanda effect valve which has a response time that is much faster than the response time of the vehicle. Slower valves would cause the vehicle to wobble or oscillate. The use of the angled jets is one of the very unique features of this robot design.

Due to the Munk moment effect described in the background above, the yaw and pitch directions of the robot are unstable. Traditionally, these directions are stabilized using fins placed in the rear of the vehicle.

In a specific embodiment, stabilizing yaw is achieved without the use of external fins. In this specific embodiment, the use of external fins is avoided by using a combination of novel design and feedback control. Nonlinear and linearized models for these dynamics are provided in Appendix B. One thing to immediately note from the state space model is the coupling between the sway velocity “v” and the yaw angle “φ.” This unusual coupling is a result of the sideslip angle. Note that if the jets were not angled to produce forces along the “y” direction, the system would be theoretically uncontrollable.

Stabilizing the pitch direction is achieved by placing the center of mass below the geometric center of the robot. Errors in the pitch direction will be eventually balanced by gravitational forces and will therefore not grow unbounded. This solution allows the maintenance of the smooth external shape.

As discussed above, the full design has been realized and tested. FIG. 10 shows drawing of the physical prototype components. In addition, videos have been made of the robot performing several unique maneuvers. Two such maneuvers are illustrated in FIGS. 11A and 11B. FIG. 11A illustrates a “forward and reverse” test where the robot is commanded to go straight forward and then straight in reverse. This type of maneuver would be difficult if not impossible for a robot that used fins to stabilize it. FIG. 11B illustrates the “sway translation” test. Essentially the robot moves sideways. Many robots are not capable of this motion. These figures have been included in this patent application to highlight how the angled jets can be used to achieve motions in both surge and sway separately.

Some advantages of the robot include an outer surface that is entirely or substantially smooth, being capable of 5 degrees of freedom, and a 90 degree pump or a retrofitted pump to achieve large forces in 2 directions using a centrifugal pump. A specific embodiment of the robot is a robot that uses an entirely or substantially smooth shape without external propellers or fins. Other advantages of the robot include water jets manipulated by valves instead of servo motors, a lack of external stabilizes, more than 3 outlet directions for jets that provide the ability to translate in the sway direction, discrete jets for steering rather than vectored thrust, two pumps, angled jets, pumps with 90 degree outlets (which provide an increase in performance over pumps with 180 degree outlets), and others.

There many commercial applications for a robot as described in this patent application. One application includes the inspection of large water filled piping systems such as those inside nuclear power plants. The robot can be equipped to carry cameras that can take pictures and video of various inaccessible areas. In addition, water transport and sewage systems also require inspection and could make use of this robot or aspects of the robot for some of their larger piping systems. Further, this robot is very quiet and highly maneuverable. Therefore it could be relevant for underwater surveillance or other naval applications.

As discussed above, a prototype of the robot has been fully built and tested. Appendix A includes some photos of a prototype. FIG. A1 shows a top view of the robot. FIG. A2 shows an end view. FIG. A3 shows a top view. FIG. A4 shows a bottom view. FIG. A5 shows a front or first end view. FIG. A6 shows a back or second end view. FIG. A7 shows a perspective view of a valve. This view shows an intake port of the valve. Also shown is a winged flapper piece (shown in black) that pivots back and forth to control the opening and closing of the valve control ports. FIG. A8 shows a top view of the valve. A coin has been included in the photograph to show the relative size of the valve. FIG. A9 shows an example of an actuation unit. The actuation unit includes a pump and two valves attached to the pump. FIG. A10 shows a diagram of the inside of the robot. Various components of the robot are shown in color for clarity. FIGS. A11-A12 show diagrams illustrating the direction of the jets. A coordinate system has been shown for orientation. As discussed above, Jets 1 and 2 are angled at their outputs (FIG. A11).

FIG. A12 shows a photograph of the inside of the robot prototype. FIGS. A14-A15 show the robot having been placed in a body of liquid (e.g., water). A movement trace has been superimposed on the photos to show the movement of the robot through the water. FIGS. A16-A17 shows a photo of forward and backward trajectory and an accompanying time graph. FIGS. A18-A19 shows another photo of movement accompanying time graph. FIGS. A20-A21 shows another photo of movement accompanying time graph. FIGS. A22-A23 shows another photo of movement accompanying time graph.

In a specific implementation, a submersible mini-robot is provided that targets inspection of nuclear reactor internals and other critical components. The robot is designed to function wirelessly and without tethers, and has the ability to move in all directions to access difficult locations. Remote-operated vehicles developed for marine applications have proven successful for the visual inspection of submerged components in nuclear reactor vessels and spent fuel pools, but commercially available technologies have several limitations. The robot, as provided in this patent application represents a step-change improvement in the nuclear power industry's underwater inspection capabilities.

The robot is designed to allow safe, reliable, and non-intrusive operation while providing high-fidelity visual inspection across a broad range of components, configurations, and locations. A prototype robot has been built and tested. This robot features a compact and appendage-free design, a high degree of maneuverability, and wireless operation. In this specific embodiment, its ovoid form measures about 4 inches by 6 inches, allowing it to nestle comfortably in the palm of a hand. Its innovative propulsion and navigation system applies centrifugal pumps, high-speed valves, and maneuvering jets for precisely controlled motion.

The robot's shape and umbilical-free operation allow for successful in-plant applications. Many existing technologies employ propellers, rudders, and other appendages and attachments that limit access to some component locations and preclude certain types of motion. These appendages also may break off during collisions or snag on obstacles, creating the potential for contamination of carefully controlled reactor environments or other operational issues. The robot as provided in this patent application has demonstrated the ability to navigate through intricate and tight geometries and to conduct inspection-type passes over surfaces.

For example, under joystick control, it can dive and rise, turn in place, and move forward, backward, and sideways. The robot is capable of carrying cameras and includes a wireless communications system. In a specific embodiment, the payload includes two cameras. The first camera supports real-time navigation and visual examination by the robot operator, and the second camera captures higher-resolution imaging data for subsequent inspection, nondestructive evaluation, and asset management applications.

Improving wireless communications for submersed usage poses challenges. Water attenuates most frequencies, and systems and components pose complex configurations. Features of the robot combine optical communication capable of high data rates at a distance with radio communication capable of two-way data exchange when line of sight is lost between the mini-robot and its controller.

In the description above and throughout, numerous specific details are set forth in order to provide a thorough understanding of an embodiment of this disclosure. It will be evident, however, to one of ordinary skill in the art, that an embodiment may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate explanation. The description of the preferred embodiments is not intended to limit the scope of the claims appended hereto. Further, in the methods disclosed herein, various steps are disclosed illustrating some of the functions of an embodiment. These steps are merely examples, and are not meant to be limiting in any way. Other steps and functions may be contemplated without departing from this disclosure or the scope of an embodiment. 

What is claimed is:
 1. An underwater robot comprising: a body comprising a first end, and a second end, opposite the first end; and first and second actuation units positioned inside the body, each actuation unit comprising a pump and two valves coupled to the pump, wherein the first and second actuation units generate jets of fluid that are discharged through the first and second ends to propel the underwater robot, and wherein the first and second ends are smooth.
 2. The underwater robot of claim 1 wherein each pump of the first and second actuation units comprises: a first exit port; and a second exit port, wherein an angle between the first and second exit ports is 90 degrees.
 3. The underwater robot of claim 1 wherein each pump of the first and second actuation units comprises a centrifugal pump.
 4. The underwater robot of claim 1 wherein each of the two valves coupled to each pump of the first and second actuation units comprises a Coanda effect valve.
 5. The underwater robot of claim 1 wherein the first and second ends do not include an appendage.
 6. The underwater robot of claim 1 wherein the first and second ends do not include a fin.
 7. The underwater robot of claim 1 wherein a shape of the first end is the same as a shape of the second end.
 8. The underwater robot of claim 1 wherein a shape of the body comprises a spheroid.
 9. The underwater robot of claim 1 comprising: a camera positioned inside the body.
 10. A underwater robot comprising: a body having a shape of a spheroid and comprising a first end, and a second end, opposite the first end; a first actuation unit to propel the underwater robot, the first actuation unit being positioned inside the body and including: a first pump having a first outlet, and a second outlet; a first valve coupled to the first outlet of the first pump; and a second valve coupled to the second outlet of the first pump; and, a second actuation unit to propel the underwater robot, the second actuation unit being positioned inside the body and including: a second pump having a third outlet, and a fourth outlet; a third valve coupled to the third outlet of the second pump; and a fourth valve coupled to the fourth outlet of the second pump, wherein an angle between the first and second outlets of the first pump is 90 degrees, and an angle between the third and fourth outlets of the second pump is 90 degrees.
 11. The underwater robot of claim 10 wherein the first and second ends do not include a fin.
 12. The underwater robot of claim 10 wherein the first and second ends are smooth surfaces.
 13. The underwater robot of claim 10 wherein a length of the body is about 146 millimeters and a width of the body is about 108 millimeters.
 14. The underwater robot of claim 10 wherein the first and second ends are symmetrical.
 15. A method comprising: placing a robot in water, wherein the robot comprises first and second actuation units to propel the robot through the water, each actuation unit including a pump having two outlets 90 degrees apart, and a valve coupled to each of the two outlets of the pump; maneuvering the robot via at least one of the first or second actuation units in a surge motion; maneuvering the robot via at least one of the first or second actuation units in a sway motion; maneuvering the robot via at least one of the first or second actuation units in a heave motion; maneuvering the robot via at least one of the first or second actuation units in a pitch motion; and maneuvering the robot via at least one of the first or second actuation units in a yaw motion.
 16. The method of claim 15 wherein the surge motion is unaccompanied by the sway, heave, pitch, and yaw motions.
 17. The method of claim 15 wherein the sway motion is unaccompanied by the surge, heave, pitch, and yaw motions.
 18. The method of claim 15 wherein the heave motion is unaccompanied by the surge, sway, pitch, and yaw motions.
 19. The method of claim 15 wherein the pitch motion is unaccompanied by the surge, sway, heave, and yaw motions.
 20. The method of claim 15 wherein the yaw motion is unaccompanied by the surge, sway, heave, and pitch motions.
 21. The method of claim 15 wherein a shape of the robot comprises a spheroid.
 22. The method of claim 15 wherein the robot does not include external propellers. 